1. Field of the Invention
This invention relates generally to a chewing gum composition which when chewed by an individual acts to remove stains and whiten tooth enamel.
2. Prior Art
A tooth is comprised of an inner layer and an outer hard enamel layer that is the protective layer of the tooth. The enamel layer of a tooth is naturally an opaque white or d slightly off-white color. It is this enamel layer that can become stained or discolored. The enamel layer of a tooth is composed of hydroxyapatit mineral crystals that create a somewhat porous surface. It is believed that this porous nature of the enamel layer is what allows staining agents and discoloring substances to permeate the enamel and discolor the tooth. Many substances that an individual comes in (contact with on a daily basis can xe2x80x9cstainxe2x80x9d or reduce the xe2x80x9cwhitenessxe2x80x9d of his or her teeth. In particular, foods, tobacco products and fluids such as tea and coffee tend to stain the teeth. These produces or substances accumulate on the enamel layer of the tooth and form a pellicle film over. the teeth. These staining and discoloring substances can then permeate the enamel layer.
Clean, white teeth are considered to be very desirable by most people in Western countries. Dull-looking, stained teeth are socially objectionable both on the basis of cosmetic appearance and also as an indication of poor oral hygiene.
There are available in the marketplace toothpaste compositions for home use which contain 1-3% b weight of peroxygen compounds such as hydrogen peroxide which when applied in a toothbrushing regimen effect whitening or removal of stains. However these toothpaste compositions are not convenient to use when outside the home.
A tooth stain-removing chewing gum which helps to keep teeth white has wide appeal to the general public. The product would be especially beneficial and convenient for use immediately after consuming stain-inducing foods, coffee, tea, red wine, and tobacco products. Since the chewing of gum is pleasurable, people normally chew for much longer periods of time than they spend brushing or flossing their teeth. Furthermore, chewing gum is especially advantageous for use when toothbrushing is not possible or convenient.
It is well known to the art that mineral adjuvants have been added to chewing gum compositions to act as cleaning and polishing agents, for example, U.S. Pat. No. 4,828,820; 4,170,632 (calcium carbonate) U.S. Pat. No. 4,400,372 (calcined kaolin) and U.S. Pat. No. 3,590,120 (zirconium silicate). The presence of the mineral adjuvants is problematic as such adjuvants are used in high concentrations in the order of 10-40% by weight and have been found to be unduly harsh to tooth enamel.
In accordance with the present invention there is provided a chewing gum composition capable of whitening and removing stain from teeth which comprises a chewing gum containing from about 0.5 to about 3.0% by weight silica particles, the particles may be precipitated, a silica gel, or a combination of the two, containing about 5 to about 35% by weight water and having:
(i) a mean particle size from about 5 to about 12 microns;
(ii) an Einlehner Hardness of from 1 to about 20;
(iii) an oil absorption value of from about 40 to less than 100 cc/100g;
(iv) a BET surface area from 100 to 700 m2/g of silica.
Mean particle size is measured using a Malvern Particle Size Analyzer, Model Mastersizer S, Malvern Instruments, Inc., Southborough, Mass. 01772 wherein a helium-neon gas laser beam is projected through a transparent cell which contains the silica particles suspended in an aqueous solution. Light rays which strike the particles are scattered through angles which are inversely proportional to the particle size. The photodetector array measures the quantity of light at several predetermined angles. Electrical signals proportional to the measured light flux values are then processed by a microcomputer system, against a scatter pattern predicted from theoretical particles as defined by the refractive indices of the sample and aqueous dispersant to determine the particle size distribution of the silica.
Einlehner hardness value is obtained using an Einlehner At-1000 Abrader to measure the softness of the silica in the following manner: A Fourdrinier brass wire screen is weighed and exposed to the action of a 10% aqueous silica suspension for a given number of revolutions. The hardness value is expressed as milligrams weight lost of the Fourdrinier wire screen per 100,000 revolutions.
BET surface area is determined by a BET nitrogen adsorption method described in Brunauer et al., J. Am. Chem. Soc., 60, 309 (1938). The BET measurement is preformed using an Accelerated Surface Area and Porosimetry Analyzer (ASAP 2400), by Micromeritics Instrument Corporation, Norcross, Ga. 30093. The sample is outgassed under vacuum at 350xc2x0 C. for a minimum of 2 hours before measurement.
Oil absorption values are measured using the ASTM rub-out method D281. All measurement levels are by weight of the total composition, unless otherwise indicated. Additionally, all measurements are made at 25xc2x0 C., unless otherwise specified.